ITV's new four part series sees the Doc Martin star embarking on an epic 10,000 mile journey across America to discover some of the biggest islands - and the lesser known hotspots too.

Martin explained: "Everyone has an image of America: A land of big shops, bright lights and asphalt highways stretching right across the continent. But there is another America – and I set out to find it."

He later added: "I wanted to look beyond corporate America and dis-cover the other United States, out past the mainland margins, and what life is like on these unique and diverse islands.

"On this island journey I meet men and women who’ve lived through many of nature’s worst extremes. And it seems one thing they all share is a profound wisdom about these challenges."

So which islands is Martin Clunes visiting? We take a look at where he's been so far and the next islands on the itinerary...

Which islands is Martin Clunes visiting?

This week sees Martin heading to the colourful Caribbean island of Puerto Rico, America's third largest island.

The island was devastated by Hurricane Maria in 2017, and Martin witnesses how local communities are beginning to recover.

He also discovers its vibrant salsa dance and music scene, learning a few steps himself!

Martin then heads on to the Sea Islands along the coast of Georgia and the Carolinas, where he meets the Gullah Geechee people, descendants of African slaves who once worked the plantations on the islands.

He then heads to Sapelo, spending time with the tiny Hog Hammock community.

A trip to Chincoteague is also on the cards to witness the iconic Chincoteague Pony Swim where local 'saltwater cowboys' herd up wild ponies and drive them through water between two islands.

Martin visits Delacroix Island (Image: Shared Content Unit)

Which islands has Martin already visited?

Last week's episode saw Martin exploring a host of breathtaking spots, kicking off his trip with a visit to the San Juan Islands in Washington State.

The actor then heads off to explore the breathtaking Channel Islands National Park, which has been dubbed 'America's Galapagos Islands' because of the spectacular and varied wildlife which resides here.

Other trips also include a visit to Avery Island to learn all about the origins of Tabasco chilli sauce, before finding out about the impact of climate change on Louisiana's island communities.

This includes the 200 flood gates which form 'The Great Wall of Louisiana', created in the aftermath of Hurricane Katrina, which can shut in the event of another hurricane.

Heading to Delacroix Island, Martin meets with locals to learn more about the area and the hurricane's impact.

Martin Clunes visits Delacroix Island (Image: Shared Content Unit)

In the first episode of the series, Martin explored the breathtaking islands of Hawaii and Alaska, arguably some of America's most famous islands.

In Hawaii, Martin discovered the impact of last year's Kilauea volcano eruption, meeting residents who were evacuated to temporary shelters.

He also explored the island of Molokai and its breathtaking Halawa Valley, one of the oldest continually inhabited human settlements in Hawaii.

North shore of Maui, Hawaii (Image: Design Pics Inc/REX/Shutterstock)

Next stop was Alaska, a stark contrast to Hawaii's hot temperatures and sandy shores; instead here he found snow-fringed glaciers.

Martin headed to the island of Kodiak in search of its legendary bear - and after six hours of waiting for a glimpse, he was rewarded with a sighting!

Where is he going next?

In the final episode of the series Martin will be heading to Manhattan Island and Ellis Island in New York.

He will also visit Coney Island before heading to Martha's Vineyard, to an island seven miles off the mainland. His final trip will take him to Maine, which has has hundreds of islands off its coast to visit the Isle au Haut.